This invention relates to an adhesive composition of general utility but possessed of certain advantageous characteristics. Adhesives formulated in accordance with the present invention have tack and rheology suitable for use in high-speed labeling equipment, are water-resistant, yet are easily cleaned off under certain conditions.
Bottled beverages such as fruit juices, soft drinks and beer are often chilled by placing them in ice water. To all concerned, it is important that the labels which identify the contents of the bottles not become detached from the bottles because of immersion.
Casein-based adhesives were developed for this type of application many years ago. However, casein is not a satisfactory raw material because of fluctuations in its availability, and, as well, differences in quality. Much work has been done with casein-based formulations, however, because of the excellent properties that some of these formulations exhibit, particularly with respect to ease of removal.
Because of dissatisfaction with the availability of casein supplies, starch-based adhesive formulations have been developed. Good formulations are disclosed, for example, in U.S. Pat. No. 3,857,803, granted Dec. 31, 1974 to R. S. Shenfeld and O. E. Brown. Generally, the formulations disclosed there comprise water, starch, a nitrogeneous substance such as urea, dicyandiamide, or a mixture of these, and an ammoniated hydrolysis product of a styrene/maleic anhydride copolymer. These formulations have excellent properties but tend to exhibit removability characteristics that are not desirable, such as, for example, the tendency to leave scum and residue on glass after removal of a label in connection with preparing the bottle for reuse.